The packaging container for milk, juice, or other drinks is obtained as follows: For example, paper/plastics laminated packaging material with crease lines are formed to a tube shape by the longitudinal seal of a longitudinal direction. The product is packed in the packaging material formed by the tube shape, the tube-like packaging material is transversally sealed in the transversal direction of the packaging material, and packaging material is formed in the primary shape of a cushion form, or pillow shape, and the packaging material is separately cut at fixed spacing (when packaging material is a web shape), and the packaging material is formed to the final shape by folding of a crease line. The final shape includes a brick shape, a multiple column, a hexagon-head column, tetrahedron shape with four triangular faces, etc.
Furthermore, with the paper packaging container of a gable top shape, a paper packaging material is cut in the predetermined shape, and the blank sealed to container lengthwise is obtained, and after sealing the bottom of a blanks within a filling machine, the product of cow's milk, juice, or other drinks is packed from the top opening, and the upper part is sealed and the container is obtained. The innermost layer of the packaging material corresponding to a transversal-seal portion or/, and a longitudinal-seal portion in the paper containers is heat sealed with the innermost layer of another side, or the outermost layer.
The low density polyethylene (LDPE) by the high-pressure method/printing ink layer/paper (fibrous) substrate layer/LDPE/aluminum foil (Al)/LDPE/LDPE, LDPE/printing ink layer/paper substrate layer/LDPE/LDPE, a printing ink layer/LDPE/paper substrate layer/LDPE/LDPE and LDPE/printing ink layer/paper substrate layer/LDPE/aluminum/polyester (PET) is known about the packaging laminate used for the conventional paper packaging container product. They are also actually used widely currently.
However, LDPE used above is high-pressure method low density polyethylene, the low molecule component contained in the high-pressure method low density polyethylene of an innermost layer bleeds to the food content in the paper container, and if it preserves at a long period of time, it has a risk that the taste of a content may change. Moreover, in the ethylene alpha olefin copolymer obtained using a Ziegler catalyst, the seal temperature is high and the processability is poor. When a lubricant is added in order to improve them, the lubricant will bleed into the food content and will reduce the taste.
The paper container with which linear low density polyethylene (LLDPE) is used for the innermost layer is proposed (JP 62-78059A, JP 60-99647A, etc.). LLDPE is very excellent in a shock intensity, a tear strength, a cold brittleness ability, a heat-sealing intensity, a hot tuck performance, etc. However, since heat-sealing start temperature is somewhat high as compared with LDPE, EVA, or an ionomer, LLDPE may be inferior in the converting properties.
On the other hand, the paper containers which has the innermost layer of the ethylene alpha olefin copolymer (the so-called metallocene PE, mLLDPE) polymerized by the metallocene catalyst are proposed (JP 7-148895A, JP 8-337237A, JP 9-29868A, JP 9-52299A, JP 9-76435A, JP 9-142455A, JP 9-86537A, JP 9-76375A, etc.). It is known that metallocene PE is good for a health performance and can be applied to a container since the metallocene PE has a low-temperature sealability, the film processability, and a narrow molecular weight distribution (WO 93/No. 08221, 44 magazine “plastic” No. 1 60 pages, 39 magazine “chemistry economy” No. 9 48 pages, 44 magazine “plastic” No. 10 83 pages). However, even though Metallocene PE has the low-temperature sealability, no metallocene PE can not necessarily make less bleeding out to the content in the paper container obtained by heat sealing. Moreover, the good performance is not shown in an extrusion laminated properties required for packaging material manufacture, and its converting properties.
If liquid food is fruit juice of citrus fruits etc., non-scalping such as a flavor and tasty, and an oxygen barrier are needed. In the liquid food, oxygen penetrates through the wall of the carton and, for the reason, those nutritional value is lost. In order to reduce permeation of the oxygen to carton and to make degradation of a nutrient like vitamin C into the minimum, usually an aluminum foil layer is added to laminated material.
In addition to above-mentioned packaging material, the strip tape covering the discontinuous section of the innermost layer between two edges of the packaging material in liquid tight can be provided in the paper packaging container formed from above-mentioned packaging material. For example, when forming web-like packaging material to a tube shape by the longitudinal seal of a longitudinal direction, packing the filled product in the packaging material, carrying out the transversal seal of the packaging material in the transversal direction and forming to a brick shape etc. finally, in order to protect the packaging material edge in a longitudinal-seal portion, the level difference section of an innermost layer is covered on a strip tape in liquid tight. Moreover, the hole usually punched at the container wall on top is formed in pouring opening of a packaging container, a spout, and pull tabs. The strip tape (a strip tape patch is included) is attached so that the punched hole may be covered.
As such a strip tape, conventionally, the strip tape of the single layer composition of the low density polyethylene (LDPE) by the high-pressure method, the strip tape which laminated LDPE to both sides on both sides of an intermediate layer's high-density polyethylene (HDPE), the strip tape which laminated LDPE to both sides on both sides of an intermediate layer's polyester (amorphous PET and PET are included), the strip tape with the LDPE laminated on both sides of an intermediate layer's polyethylene vinyl alcohol (EVOH) are used, or are proposed.
Moreover, the various trials in which the practical substitute which changes to aluminum foil is developed have been made. Moreover, it can be scrapped after use, it being provided with the outstanding oxygen gas barrier, and perfume barrier properties. Using the vapor deposited layer of an inorganic oxide for the packaging material for paper containers was proposed (JP,5-28190,Y, JP,8-500068,A, JP,6-93120,A). By the packaging material which has such a gas (oxygen) barrier, the paper container which has a non-scalping or quality keeping ability can be offered. In filling/packing process of liquid food, the surface portion to be sealed is polluted with an oxide by the temperature of the fused extrusion heat in the extrusion lamination step. Moreover, the surface is polluted with remains liquid food. It becomes important in an actual manufacturing process to optimally seal the packaging material to which such a contaminant and an impurity exist in the surface. In the above-mentioned conventional liquid food paper container packaging material, it is difficult to obtain the optimal seal.
In the filling packaging method of a brick shape packaging container, the innermost layer of one edge of packaging material and the outermost layer of the edge of another side are longitudinally sealed for the packaging material of a continuation paper substrate layer with a crease line. The packaging material is formed in the longitudinal direction at a tube shape, and filled liquid food is packed in tube-like packaging material. The innermost layer of tube-like packaging material is sealed with each other under the surface of this liquid food, and the transversal seal of the packaging material is carried out in the transversal direction for every predetermined spacing. The packaging material is cut along with a transversal-seal portion, it forms in primary shape, the packaging material is formed by folding in alignment with the crease line in the final shape of a brick shape, and a packaging container is obtained. It is difficult to obtain a good seal by the filling packaging method, since the packaging material is sealed under the surface of liquid food, liquid food surely remains and the surface is polluted.
Furthermore, since filling liquid food has various quality and properties about temperature, the temperature conditions when filling with and packaging the food are changed broadly, therefore the temperature of the filling step is influenced and is changed in the range also with the large seal temperature in the process of filling and packaging. However, since the heat adhesive resin in the conventional packaging material does not necessarily have the seal properties of a large temperature range, the temperature of a filling content influences and a good seal is not obtained.
Moreover, in the multi-purpose conventional thermoplastic polymer for seals mentioned above, there is a risk that this thermoplastic material layer may melt, a pinhole, foaming, a blister, etc. may happen in some layers, and seal strength may decrease remarkably, and a liquid content may leak from the poor portion, by for example, the elevated-temperature air under the sealing step. If the layer of a thermoplastic material is thickened in order to prevent them, the container cost rises inconveniently.